function countDown(time) {
    var nowTime = new Date();
    var overTime = new Date(time);
    var times = (overTime - nowTime)/1000;
    var d =parseInt(time / 60 /60 / 24);
    d=d<10? '0' +d:d;
    var h = parseInt(time /60 /60%24);
    h =h<10?'0'+h:h;
    var m = parseInt(time /60 %60);
    m =m<10?'0'+m:m;
    var s = parseInt(time %60 );
    s=s<10?'0'+s:s;
    return d +'天'+h+'时'+m+'分'+s+'秒';
}
console.log(countDown('2021-9-25 09:00:00'));